Humidity and Clouds

Clouds and Relative Humidity

Multiple Choice

When something evaporates

• it releases heat and has a warming effect

• It absorbs heat and has a cooling effect

• It absorbs heat and has a warming effect

• It releases heat and has a cooling effect

Open Ended

Why do you feel cooler when sweat evaporates off your skin? Use evidence from the video to support your claim.

Clouds

Have you ever looked at the sky and found shapes in the clouds?Clouds have a great effect on the weather and climate, but they can also be lovely (if they're not pouring rain on you). It's fun to sit and watch the clouds go by.

Humidity

Humidity is the amount of water vapor in the air in a particular spot. We usually use the term to mean relative humidity, the percentage of water vapor a certain volume of air is holding relative to the maximum amount it can contain. If the humidity today is 80%, it means that the air contains 80% of the total amount of water it can hold at that temperature. What will happen if the humidity increases to more than 100%? The excess water condenses and forms precipitation.

Open Ended

Give your own definition for relative humidity:

Since warm air can hold more water vapor than cool air, raising or lowering temperature can change air's relative humidity (Figure to the right). The temperature at which air becomes saturated with water is called the air's dew point. This term makes sense, because water condenses from the air as dew if the air cools down overnight and reaches 100% humidity.

Multiple Choice

What type of air holds more water vapor?

• Warm air

• Cool air

Multiple Choice

What does the relative humidity need to be in order for cloud formation and precipitation to occur?

• 25%

• 50%

• 75%

• 100%

Multiple Choice

Changing what factor can change the relative humidity of air?

• temperature

• dew point

• gravity

• Black Hole

Multiple Choice

When the air temeperature reaches the dewpoint ________________ occurs.

• evaporation

• condensation

• transpiration

• percolation

Multiple Choice

In order for air to reach the dew point the relative humidity of the air needs to be

• 20%

• 50%

• 75%

• 100%

Multiple Choice

When air reaches 100% relative humidity, that means it cannot hold any more moisture. Do you think that more water can evaporate into the air at that point?

• Yes

• No

Multiple Choice

What is the relative humidity when the dry-bulb temperature is 16°C and the wet-bulb temperature is 14°C?

• 90%

• 80%

• 14%

• 13%

Multiple Choice

When the dry-bulb temperature is 14°C and the wet-bulb temperature is 8°C, the relative humidity is

• 6%

• 22%

• 25%

• 41%

Multiple Choice

What is the approximate dewpoint temperature when the dry-bulb reading is 14ºC and the wet-bulb reading is 8ºC?

• 1ºC

• 6ºC

• –6ºC

• –9ºC

Multiple Choice

What is the dewpoint temperature when the dry-bulb

temperature is 12ºC and the wet-bulb temperature is

7ºC?

• 1ºC

• -2ºC

• -5ºC

• 4ºC

Multiple Choice

What is the approximate dewpoint temperature if the

dry-bulb temperature is 18ºC and the wet-bulb

temperature is 11ºC?

• 1º C

• -10º C

• 7º C

• 4º C